Hey Tom, Thanks for the KIP. It seems that the prior discussion in this thread has focused on reassigning partitions (or AlterTopics). I haven't looked into this yet. I have two comments on the replicaStatus() API and the ReplicaStatusRequest:
- It seems that the use-case for ReplicaStatusRequest is covered by the DescribeDirsRequest introduced in KIP-113 <https://cwiki.apache.org/confluence/display/KAFKA/KIP-113%3A+Support+replicas+movement+between+log+directories>. DescribeDirsResponse contains the logEndOffset for the specified partitions. The the lag of the follower replica can be derived as the difference between leader's LEO and follower's LEO. Do you think we can simply use DescribeDirsRequest without introducing ReplicaStatusRequest? - According to the current KIP, replicaStatus() takes a list of partitions as input. And its output maps the partition to a list of replica status. Do you think it would be better to have a new class called TopicPartitionReplica, which identifies the topic, partition and the brokerId. replicaStatus can then take a list of TopicPartitionReplica as input. And its output maps the replica to replica status. The latter API seems simpler and also matches the method name better. What do you think? Thanks, Dong On Wed, Aug 2, 2017 at 5:12 AM, Tom Bentley <t.j.bent...@gmail.com> wrote: > Hi again Ismael, > > > 1. It's worth emphasising that reassigning partitions is a different > >> process than what happens when a topic is created, so not sure trying to > >> make it symmetric is beneficial. In addition to what was already > >> discussed, > >> one should also enable replication throttling before moving the data. > > > > > > Thanks for your responses.The only advantage I can see from having > > separate APIs for partition count change vs. the other changes is that we > > expect the former to return synchronously, and the latter to (usually) > > return asynchronously. Lumping them into the same API forces clients of > > that API to code for the two possible cases. Is this the particular > concern > > you had in mind, or do you have others? > > > > Just to help see what this looks like I've created another version of > KIP-179 ( > https://cwiki.apache.org/confluence/display/KAFKA/Copy+ > of+KIP-179+-+Change+ReassignPartitionsCommand+to+use+AdminClient > ). > > The AdminClient APIs are more type safe (harder to misuse). The > asynchronous nature of the alterReplicationFactors() and > reassignPartitions() methods aren't really apparent (you'd still have to > read the javadocs to know you had to call replicaStatus() to determine > completion), but it's still better that the lumped-together API because the > methods are _consistently_ async. The Protocol APIs are slightly nicer too, > in that INVALID_REQUEST is less commonly returned. Another benefit is it > would allow for these different alteration APIs to be modified > independently in the future, should that necessary. > > What do others think? > > You're right that the proposal doesn't cover setting and clearing a > > throttle, and it should. I will study the code about how this works > before > > posting back about that. > > > > AFAICS from the code the throttle is simply a dynamic config of the broker. > We already have the AdminClient.alterConfigs API for setting this, so the > refactoring of kafka-reassign-partitions.sh could just use that existing > API. We could still achieve your objective of setting the throttle before > reassignment by making the --throttle option mandatory when --execute was > present. Or did you have something else in mind? > > Thanks, > > Tom >
